E-mail is a well-established process of sending a text message from a sender to a recipient. The process of conventional e-mail is defined by a number of different interacting protocols and servers.
In conventional e-mail, a personal computer 100 runs an e-mail client 102. Well-known e-mail clients include Microsoft outlook and Outlook express. The e-mail client may be a standalone client, or may be a modified e-mail client running within a web page such as “Hotmail”. The e-mail client lists the messages in the user's mailbox by headers, and allows the user to select and read the e-mail that is associated with that header. An e-mail client also allows creation of new messages and sending of the new messages.
The e-mail client communicates with an e-mail server 120 at the user's local Internet Service provider, here shown as “domain” 99, in order to send and receive messages over the Internet 110 or more generally over any network connection. A domain can include a single mail cluster, e.g., all of hotmail.com, or can include multiple mail clusters that are somehow associated.
The server receives e-mail messages from a client 102, and forms a list of those messages. The server 120 typically includes a processor or computer of some type, running the special email programs that are described herein.
The mechanics of the e-mail system operate by using three different protocols, known as SMTP, POP3 and IMAP. The SMTP server listens on port 25 to receive incoming emails. The POP3 server 140 handles delivery of local messages to the local mailboxes, such as 145. The mailbox is really a queue that is formed to provide the message an email client, when that client logs in to the POP3 server 140 at the domain 99.
Sending emails is handled differently than receiving emails. In order to send an e-mail, the e-mail client 102 interacts with the SMTP server 130 at the domain 99. If the message is intended for another mailbox within the same domain, then the SMTP server 130 sends the message to the local POP3 server 140. If the message is intended for another domain, the SMTP server communicates with a domain name server or DNS 135. The DNS stores a database, which is updated from the Internet, that stores the IP address for all domains. The DNS provides the IP address to the SMTP server 130.
The messages are stored on the hard drive 131 of the SMTP server 130. Software called a “picker” often operates to streamline the operations. The picker looks at messages stored on the SMTP server's hard drive 131, and carries out the mechanics of analyzing the message headers for destination, communicating with the DNS, and looking for an available port for the SMTP server on the destination domain.
Once these operations are completed, the SMTP server 130 sends the message using the IP address that it obtained from the DNS server 135 to another SMTP server 150 at the destination domain 149. The SMTP server 130 communicates with the corresponding SMTP server 155 at domain 149. The message is transferred to the SMTP server 155 at domain 149. Since SMTP server 155 recognizes that the message is for a local mailbox, it provides the message to its local POP3 server 160 which queues the message to a local mailbox 165.
Sending email often uses an open-source program known as Sendmail™ which also includes many additional capabilities, including the ability to queue messages which cannot be sent immediately.
The receiving of emails uses POP3 server. The POP3 server maintains a collection of text files, one for each e-mail that has been sent or received. Each time a new e-mail is received, it adds that e-mail to its recipient file, or mailbox. The e-mail client 102 communicates with the POP3 server 140 at the local domain 99. The POP3 server provides the e-mail client 102 with contents of its mailbox, and then deletes the messages.
An IMAP server may be used in addition to or in place of POP3. IMAP allows the e-mail into folders which stay on the server.
For a large e-mail server, there may be many pickers operating at once, e.g. 50 to 100 pickers. Each of these pickers are obtaining information from the SMTP server's hard drive 131, moving messages one at a time from the hard drive.